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In real-world production and applications, sacrificial anodes are widely recognized for their remarkable performance and corrosion protection capabilities. However, without a proper understanding of the product’s actual properties and working conditions, its effectiveness may not be fully realized — since sacrificial anodes themselves are also subject to oxidation. The following explanation from industry experts will clarify the key factors influencing oxidation time.
Experts engaged in the development and production of aluminum alloy anodes explain that sacrificial anode protection is a common electrochemical method used in industrial processes. The materials used as sacrificial anodes must meet several essential requirements:
they should have a sufficiently negative and stable potential, a low and uniform self-corrosion rate, high and stable current efficiency, high electrochemical equivalent (meaning a large current per unit mass), small anodic polarization, uniform dissolution, easily detachable corrosion products, and must not cause environmental pollution.
Currently, in practical applications, the selection of sacrificial anodes depends on their shape and electrode potential differences. In soils or freshwater environments with resistivity ranging from 20–50 Ω·m, the potential of sacrificial anodes is typically around –1.75 V (CSE), with an activation voltage of 0.85 V. Different environments require different anode materials and specifications.
In actual use, sacrificial anodes provide excellent protection to equipment. However, during the oxidation process, the duration of oxidation must be carefully controlled:
if the oxidation time is too short, the oxide film becomes thin and smooth; if too long, the film may become porous. Therefore, understanding the optimal oxidation time is critical.
Pre-treatment Stage:
After 25 minutes of pre-treatment, when the current density stabilizes at 2.5–3 A/dm², the film growth officially begins. If this duration is too long or too short, product quality will be negatively affected. The optimal time should be strictly followed as specified in each process standard.
Oxidation Ramp-up Stage:
Once the component enters the oxidation bath, an initial current density of 0.5 A/dm² should be applied. Over the next 25 minutes, the current density should be gradually increased in 5–8 steps from 0.5 A/dm² to 2.5 A/dm².
If this process is rushed, short circuits and burning may occur during film formation. If prolonged excessively, it becomes unnecessary and inefficient.
In conclusion, oxidation time plays a decisive role in the performance of sacrificial anodes. Excessive or insufficient oxidation will both lead to poor quality. Only by maintaining precise control over oxidation duration can the sacrificial anode deliver its intended protective effect.
